Hitherto, as a mold for producing heat resistant plastic moldings having perforations, an ordinary steel mold for dies and a simple mold by a low melting metal has been used.
The aforesaid mold is properly selected according to the form of a desired molded product and, in particular, in the case of producing moldings having many small holes, the mold for use is usually composed of a fixed metal platen, a stripper metal platen, and a movable metal platen, wherein the cavity for molding is formed by the fixed metal platen and the stripper metal platen having perforations for passing hard metal pins disposed between the fixed metal platen and the stripper platen, small holes of the molded product are formed by the pins of a hard metal pin fixed platen equipped to the movable platen, and drawing of the hard metal pins for forming small holds from the molded product is performed by the stripper platen.
However, in the case of making such a mold of the type of forming the above-described molding cavity by steel, there is a disadvantage indispensably requiring working of many fine holes, fixing the hard metal pins for forming fine holes, surface working, etc., which are very troublesome in working and accuracy as well as from an economical viewpoint. Also, in the case of a low melting metal, it is required that for the portion of forming perforations, the hard metal pins are fixed in the pin-fix platen but there is a disadvantage that the hard pins thus fixed in are liable to be loosened by the action of heat or pressure.